Around Labor Day or the few weeks that follow are the best times to seed your yard in Minnesota because the weather is starting to cool down and there is dew present most mornings. Also any pre-emergents you may have used in the spring have had time to work their way out of the soil.
As a homeowner, there are a couple of essential steps you can take to take to prep your lawn. The first is eliminating any remaining summer weeds (oxalis, spurge, purslane, quackgrass or crabgrass). The first three can usually be taken care of with a selective herbicide that contains 2,4-D. Use a selective post-emergent for annual grasses to treat crabgrass. Quackgrass, however, will need to either be pulled by hand or carefully taken care of with a non-selective such as Round-Up. When using any of these products, make sure they work out of the soil within two weeks, or you run the risk of putting down seed that will never germinate.
The second step is prepping your yard to create the best seed-to-soil contact. With patchy lawns, putting down topsoil with seed is a great way to fill in bare areas. For healthy yards, dethatching or aerating first will considerably increase the percentage of seed germination.
The final process of laying seed comes after the lawn has been dethatched or aerated. For Minnesota, Kentucky Bluegrass, fine Fescue, and a perennial Ryegrass mix will suit most lawns. Use a dense shade mix if your lawn calls for it. Because it only requires a few hours of light per day, Red Fescue should be present in the mix for shaded lawns. Finally, pick up a quality seed that does not contain much filler. Stay away from the easy-seed and patching mixes because they are only meant to fill in small spaces such as pet spots. These easy steps can ensure that the grass is always greener on your side.